A record number of migrants – more than 10,000 – were recently apprehended at the US-Mexico border in a 24-hour period, fuelling fears over what comes next when a controversial immigration policy expires this week.

Nowhere are the realities of what some have termed a border “crisis” more evident than in the Texas city of El Paso.

Here, migrants – many of them confused about the impending rule changes – have been left sleeping rough in makeshift campsites on city streets over the last several days.

Several thousand were camped out earlier this week around a single church in the city centre.

“We’ve never seen this before,” Mayor Oscar Leeser said at a border security expo just streets away from the campsite on Wednesday. “Something has to change. As a community, we can’t do this forever.”

The worst, officials say, may be yet to come.

US President Joe Biden earlier this week acknowledged that the border would be “chaotic for a while” despite the best efforts of authorities.

First implemented in 2020, Title 42 allows US authorities to swiftly expel would-be migrants attempting to cross the border from Mexico – including those seeking humanitarian asylum – using the Covid-19 pandemic as justification.

But with the policy due to expire a minute before midnight on 11 May, officials fear border authorities may be overwhelmed by an influx of migrants even as record numbers in recent years have already strained resources and left border towns scrambling for solutions.

Mr Leeser warned that across from El Paso alone, an estimated 10,000 migrants were “lined up at the border, waiting to come in”.

In a bid to stop the flow, the Biden administration introduced strict new rules for asylum seekers on Wednesday, including barring those who cross illegally from applying from asylum for five years.

US officials have also announced new changes aimed at encouraging migrants to seek legal pathways to the country, as well as strict penalties and swift deportation for those who cross illegally.

Additionally, about 24,000 law officers have been stationed along the length of the 2,000 mile (3,218km) border, along with thousands of National Guard troops and active-duty military personnel sent to help Customs and Border Protection (CBP).

The new measures come amid an increased burden on CBP. In the El Paso sector alone, officials say that officers have recorded 265,000 migrant “encounters” since the current fiscal year began on 1 October – an 134% increase from the prior year. Currently, officers in the area are averaging about 1,700 migrant detentions daily.

More than 27,000 migrants were in US custody at one time earlier this week, well above CBP’s existing capacity to house them. To cope with the migrants on city streets, on Tuesday CBP and El Paso police launched an “enforcement” operation asking migrants to head to the nearest CBP facility for processing.

Migrants in the area also said that some had run, fearful of deportation, while others had reluctantly presented themselves to CBP officers in the hopes that they would be allowed to stay.

Speaking on Wednesday, Homeland Security Secretary Alejandro Mayorkas said that much of the problem stemmed from smugglers who had “been hard at work spreading false information that the border will be open” after 11 May.

“It will not be. They are lying,” he added. “We urge migrants once again not to believe the smugglers who are lying to them solely to make a profit. We are building lawful pathways for you to come to the United States.”

Among the steps being taken are the opening of regional processing centres aimed at helping migrants apply to come to the US, as well as expanded access to CBP One, an app which migrants can use to schedule asylum appointments.

CBP also plans to ramp up efforts to counter misinformation to combat rumours about border policies.